I have the same problem. Some years back I bought a 2 piece set of leathers and the trousers were too long, I took them to "Leather Man Dave" (Bradford, West Yorkshire) He said the problem is from the hip to the knee, not the length of the trousers.
Anyway, he unpicked them at the knee, took 40mm off the hip to knee section and put them back together, hey presto, knee pads in their correct place, perfect length in the leg. They were so good and comfortable I kept them for nearly 10 years.
Dave was so good, if you bought Hien Gericke gear and he did any alterations they would keep the guarantee..

So, not the easiest or cheapest solution but If you buy expensive gear and intend to keep it a while, it's worth considering.

windy